In the data communication field involving computers and networking, there is a basic concept of the "dialog", which in computing circles, involves the exchange of human input and the immediate machine response that forms a "conversation" between an interactive computer and person using it. Another aspect of the "dialog" is the reference to the exchange of signals by computers communicating on a network. Dialogs can be used to carry data between different application processes, and can be used to carry data over computer networks. In computer networking, dialogs can be considered to provide data communication between application processes running on different systems or different hosts. Further, dialogs can carry data between application processes running on the same host.
There is a generally recognized OSI (Open System Interconnection) standard for worldwide message transfer communications that defines a framework for implementing transfer protocols in 7 layers. Control is passed from one layer to the next, starting at the layer called "the Application Layer" in one station, proceeding to the bottom layer, over the channel to the next station, and back up the layers of a hierarchy which is generally recognized as having 7 layers. Most of all communication networks use the 7-layer system. However, there are some non-OSI systems which incorporate two or three layers into one layer.
The layers involved for network Users are generally designated from the lowest layer to the highest layer, as follows:
1. The Physical Layer; PA1 2. The Datalink Layer; PA1 3. The Network Layer; PA1 4. The Transport Layer; PA1 5. The Session Layer; PA1 6. The Presentation Layer; and PA1 7. The Application Layer.
The Application Layer 7 (top layer) defines the language and syntax that programs use to communicate with other programs. It represents the purpose of communicating. For example, a program in a client workstation uses commands to request data from a program in a server. The common functions at this Application Layer level are that of opening, closing, reading and writing files, transferring files and e-mail, executing remote jobs, and obtaining directory information about network resources.
The Presentation Layer 6 acts to negotiate and manage the way the data is represented and encoded between different computers. For example, it provides a common denominator between ASCII and the EBCDIC machines, as well as between different floating point and binary formats. This layer is also used for encryption and decryption.
The Session Layer 5, coordinates communications in an orderly manner. It determines one-way or two-way communications, and manages the dialog between both parties, for example, making sure that the previous request has been fulfilled before the next request is sent. This Session Layer also marks significant parts of the transmitted data with checkpoints to allow for fast recovery in the event of a connection failure. Sometimes the services of this session layer are included in the Transport Layer 4.
The Transport Layer 4, ensures end to end validity and integrity. The lower Data Link Layer (Layer 2) is only responsible for delivering packets from one node to another). Thus, if a packet should get lost in a router somewhere in the enterprise internet, the Transport Layer will detect this situation. This Transport Layer 4 ensures that if a 12 MB file is sent, the full 12 MB will be received. OSI transport services sometimes will include layers 1 through 4, and are collectively responsible for delivering a complete message or file from a sending station to a receiving station without error.
The Network Layer 3 routes the messages to different networks. The node-to-node function of the Datalink Layer (Layer 2) is extended across the entire internetwork, because a routable protocol such as IP, IPX, SNA, etc., contains a "network address" in addition to a station address. If all the stations are contained within a single network segment, then the routing capability of this layer is not required.
The Datalink Layer 2 is responsible for node-to-node validity and integrity of the transmission. The transmitted bits are divided into frames, for example, an Ethernet, or Token Ring frame for Local Area Networks (LANs). Layers 1 and 2 are required for every type of communication operation.
The Physical Layer 1 is responsible for passing bits onto and receiving them from the connecting medium. This layer has no understanding of the meaning of the bits, but deals with the electrical and mechanical characteristics of the signals and the signaling methods. As an example, the Physical Layer 1 comprises the RTS (Request to Send) and the CTS (Clear to Send) signals in an RS-232 (a standard for serial transmission between computers and peripheral devices) environment, as well as TDM (Time Division Multiplexing) and FDM (Frequency Division Multiplexing) techniques for multiplexing data on a line.
It will be seen that present-day communication systems generally will have a high band-pass capability of data throughput for high speed network technologies which may occur at rates on the order of 100 MB per second, to 1 gigabit per second.
However, sometimes the problems of delays or latency may be high. Latency is generally considered to be the time interval between the time a transaction issues and the time the transaction is reported as being completed. In certain systems having a high latency, the round-trip time for two clients communicating with each other to complete a data request can be on the order of milliseconds.
The delays in communication due to "latency" will be seen to occur from conventional communication systems due partly to overhead in the communication layers, and generally is especially due to latency in the layers below the Transport Layer 4, i.e., Layers 3, 2 and 1.
In high speed data communication systems, the Transport Layer 4 is still seen to impart substantial latency in communications.
The present method and system describes the functions and sequential operations for and Output Interface of a Cooperative Service Interface between Network Providers and their Users, such as DSSs (Distributed System Service) units which enhances the speed of dialog exchanges and this improves communication system performance. Further, the present Output Interface is used to supersede previously used sync Port Interfaces which had a number of latency problems. The sync Port Interfaces used an earlier Connection Block technology which had extra sublayers in the data path and had locking protocols which were not integrated so that each module had its own private lock which required considerable time to be spent in locking, unlocking and synchronization.